Add shuffle operator to pixels.

Base/include/Pixel.h

@@ -143,6 +143,17 @@ class Pixel : public Vector4<uint16> {
   uint32 Pack() const;
   void Unpack(uint32 rgba);
 
+  // Shuffles the pixel values around so that they change their ordering based
+  // on the passed mask. The values are chosen such that each two bits from the
+  // least significant bit define a value from 0-3. From LSB to MSB, the values
+  // are labelled a, b, c, d. From these labels, we store:
+  // m_Pixels[0] = m_Pixels[a]
+  // m_Pixels[1] = m_Pixels[b]
+  // m_Pixels[2] = m_Pixels[c]
+  // m_Pixels[3] = m_Pixels[d]
+  // hence, 0xE4 (11 10 01 00) represents a no-op.
+  void Shuffle(uint8 shuffleMask = 0xE4);
+
   // Tests for equality by comparing the values and the bit depths.
   bool operator==(const Pixel &) const;
 };

Base/src/Pixel.cpp

@@ -222,6 +222,29 @@ namespace FasTC {
     B() = ChangeBitDepth((rgba >> 16) & 0xFF, 8, m_BitDepth[3]);
   }
 
+  void Pixel::Shuffle(uint8 shuffleMask) {
+    Pixel thisPixel(*this);
+    uint8 a = shuffleMask & 3;
+    uint8 b = (shuffleMask >> 2) & 3;
+    uint8 c = (shuffleMask >> 4) & 3;
+    uint8 d = (shuffleMask >> 6) & 3;
+
+    Pixel tmp;
+    tmp[0] = thisPixel[a];
+    tmp.m_BitDepth[0] = thisPixel.m_BitDepth[a];
+
+    tmp[1] = thisPixel[b];
+    tmp.m_BitDepth[1] = thisPixel.m_BitDepth[b];
+
+    tmp[2] = thisPixel[c];
+    tmp.m_BitDepth[2] = thisPixel.m_BitDepth[c];
+
+    tmp[3] = thisPixel[d];
+    tmp.m_BitDepth[3] = thisPixel.m_BitDepth[d];
+
+    *this = tmp;
+  }
+
   bool Pixel::operator==(const Pixel &other) const {
     uint8 depths[4];
     other.GetBitDepth(depths);